title: Association of botulinum neurotoxin serotype A light chain with plasma membrane-bound SNAP-25.
abstract: The Clostridium botulinum neurotoxins (BoNTs) cleave SNARE proteins, which inhibit binding and thus fusion of neurotransmitter vesicles to the plasma membrane of peripheral neurons. BoNTs comprise an N-terminal light chain (LC) and C-terminal heavy chain, which are linked by a disulfide bond. There are seven serotypes (A-G) of BoNTs based upon immunological neutralization. Although the binding and entry of BoNT/A into neurons has been subjected to considerable investigation, the intracellular events that allow BoNT/A to efficiently cleave SNAP-25 within neurons is less well understood. Earlier studies showed that intracellular LC/A bound to the plasma membrane of neurons. In this study, intracellular LC/A is shown to directly bind SNAP-25 on the plasma membrane. Solid phase binding showed that the N-terminal residues of LC/A bound residues 80-110 of SNAP-25, which was also observed in cultured neurons. Association of the N-terminal 8 amino acids of LC/A and residues 80-110 of SNAP-25 also enhanced substrate cleavage. These findings explain how LC/A associates with SNAP-25 on the plasma membrane and provide a basis for LC/A cleavage of SNAP-25 within the SNARE complex.
authors.affiliation: Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom Kowloon, Hong Kong.
authors.forename: Sheng
authors.initials: S
authors.lastname: Chen
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Barbieri
mesh_terms: D000818:Animals; D001665:Binding Sites; D019274:Botulinum Toxins, Type A / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D003014:Clostridium botulinum / Q000378:metabolism*; D006868:Hydrolysis; D051379:Mice; D009474:Neurons / Q000378:metabolism; D009498:Neurotoxins; D011485:Protein Binding; D050825:Synaptosomal-Associated Protein 25 / Q000378:metabolism*
chemical_list: D009498:Neurotoxins; C494209:Snap25 protein, mouse; D050825:Synaptosomal-Associated Protein 25; D019274:Botulinum Toxins, Type A